DEFAULT-PRINT-PROMPT

The prompt printed by ACL2 displays the current package, followed by
a space, followed by zero or more of the three characters as
specified below, followed by the character > printed one or more
times, reflecting the number of recursive calls of ld. The three
characters in the middle are as follows:

p ; when (default-defun-mode (w state)) is :program
! ; when guard checking is on
s ; when (ld-skip-proofsp state) is t